In recent times, the use of femtocell basestations has been proposed, for use in cellular communications networks. Such femtocell basestations may typically be purchased by a user for use in an office or home, where they can be connected to a core network through the internet. Thereafter, the femtocell basestations act as regular basestations within the cellular network, and provide service for mobile phones (UEs) within that office or home.
Femtocells typically have a restricted number of dedicated (pre-provisioned) users to which they individually provide service. Local Access Control procedures in the femtocell restrict service to only those users that are provisioned/authorised on that femtocell.
Mobiles (referred to as UEs henceforth) are able to discern whether they can access any cell based on PLMN codes (from their home PLMN or other permitted/equivalent PLMN). However, for cells within the allowed PLMN code(s), UEs are typically unable to ascertain which femtocells they will or will not be granted service on. Therefore UEs will typically attempt to register for service on any otherwise suitable femtocell.
The “Home” femtocell(s) (defined as one or more cells where that UE is specifically provisioned for service) will accept the registration and provide service. However any “visited” femtocell (defined as any cell where the UE is not provisioned for service) will reject the registration attempt.
This restricted number of authorized users leads to many problems that are not typically encountered with conventional basestations within the cellular network.